The influence of precipitation on the energy footprint of Denver's water supply: A 20-year analysis and implications for climate change

Abstract

Denver Water serves 1.5 million people in the metropolitan area of Denver, Colorado, USA. Relying on runoff from mountain watersheds, its water supply is obviously sensitive to precipitation, but so is its energy footprint. We analyzed Denver Water's annual energy use and water use alongside local precipitation over a 20-year period from 1995 to 2014. Energy use generally trended opposite to precipitation: In dry years the system used more energy than in wet years, even when the energy use was normalized by water volume. The data suggest that the system needs to compensate for less precipitation by expending more energy, presumably by supplying water from more distant or more energy-intensive water sources. A regression model indicates that a 1 cm decrease in annual precipitation equates to 275,000 kWh of additional energy use and that typical interannual variability in precipitation accounts for 11% of Denver Water's energy footprint. The analysis highlights implications for altered energy footprints as water utilities respond to new precipitation patterns in a changing climate.